From German Patent DE 29 44 319 A1 a gas bag restraint system is known with a gas bag which can take up various volumes depending on the intensity of the impact. In the non-unfolded state, two chambers are provided, with a tear seam connecting opposite sections of the outer wall with each other. Thereby, only one chamber can be inflated when the interior pressure of the gas bag is not sufficient to destroy the tear seam. In the case of a collision with high impact intensity, the internal pressure in the gas bag is increased so that the tear seam is destroyed and the gas bag can take up a greater volume. In this case, not two chambers are formed, but rather one large chamber is produced. A problem of the gas bags known hitherto consists in that the abruptly unfolding gas bag strikes against an occupant sitting close to the restraint system and not yet moving forward relative to the vehicle. In addition, in fully inflated state when the occupant falls into it, the gas bag is relatively hard.
A further gas bag restraint system is shown in the DE 92 11 421 U1. This gas bag restraint system comprises a gas bag with two chambers, one chamber, namely the greater of the two, offering protection at the primary impact of the vehicle occupant and thereafter collapsing relatively quickly. The second chamber, on the other hand, collapses distinctly later than the first chamber, so that in the case of a secondary impact the vehicle occupant does not hit against hard parts such as the gas generator. In this known restraint system, always both chambers are unfold. Valve flaps on the dividing wall between the first and the second chamber permit a passage of gas exclusively from the first into the second chamber.